Binder Resin Composition for Nonaqueous Electrolyte Energy Device Electrode, Nonaqueous Electrolyte Energy Device Electrode, and Nonaqueous Electrolyte Energy Device

a technology of nonaqueous electrolyte energy device electrode and binder resin, which is applied in the direction of non-aqueous electrolyte cells, cell components, electrochemical generators, etc., can solve the problems of impede the effort to raise the capacity of lithium batteries, poor adhesion of pvdf, and insufficient pvdf, etc., to achieve excellent adhesion, excellent resistance to swelling, and high capacity

Active Publication Date: 2008-01-03
RESONAC CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0019] The binder resin composition according to the present invention for a nonaqueous electrolyte energy device, because it has a copolymer structure from a nitrile group-containing monomer, a soft and flexible relatively long-chain monomer containing an oxyethylene skeleton and / or monomer containing a relatively long-chain alkyl group, and optionally a highly adhesive carboxyl group-containing monomer, exhibits an excellent adhesiveness for the negative electrode current collector and an excellent resistance to swelling by liquid electrolyte and provides a soft and flexible electrode. As a consequence, a lithium battery that is a nonaqueous electrolyte energy device that uses an electrode fabricated using the binder resin composition according to the present invention, will have a high capacity and will present little decline in capacity during charge-discharge cycling.

Problems solved by technology

However, PVDF exhibits a poor adhesiveness for the negative electrode current collector (copper foil), and, when a negative electrode is fabricated using PVDF, it therefore becomes necessary to blend large amounts of PVDF relative to the negative electrode active material in order to secure adhesion at the interface between the composite layer and current collector, which impedes the effort to raise the capacity of lithium batteries.
Moreover, PVDF is not always sufficiently resistant to swelling by the liquid electrolyte (liquid that mediates lithium ion transfer between the positive and negative electrodes during charge / discharge) used in lithium batteries, and when as a consequence the PVDF in the composite layer is swollen by the liquid electrolyte, the composite layer / current collector interface is loosened up, as is contact by the active material with itself in the composite layer.
This leads to a gradual disruption of the conductive network in the electrode and has been a factor in causing a timewise decline in capacity during the repetitive charge-discharge cycling of lithium batteries.
However, poly(meth)acrylonitrile is inherently a polymer with a rigid molecular structure, and the copolymers with short-chain monomer as described in the aforementioned documents create problems with regard to the softness and flexibility of the resulting electrode, even when a rubbery component is blended therein.
This has created the risk of the generation of defects, for example, cracking in the composite layer, during the fabrication of lithium battery electrodes, for example, during roll press molding or during the step in which the positive electrode and negative electrode are wound with an interposed separator into a coil.

Method used

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  • Binder Resin Composition for Nonaqueous Electrolyte Energy Device Electrode, Nonaqueous Electrolyte Energy Device Electrode, and Nonaqueous Electrolyte Energy Device
  • Binder Resin Composition for Nonaqueous Electrolyte Energy Device Electrode, Nonaqueous Electrolyte Energy Device Electrode, and Nonaqueous Electrolyte Energy Device
  • Binder Resin Composition for Nonaqueous Electrolyte Energy Device Electrode, Nonaqueous Electrolyte Energy Device Electrode, and Nonaqueous Electrolyte Energy Device

Examples

Experimental program
Comparison scheme
Effect test

example 1

[0057] A reaction solution was prepared by introducing, under a nitrogen blanket, 45.0 g acrylonitrile (nitrile group-containing monomer, from Wako Pure Chemical Industries, Ltd.), 5.0 g lauryl acrylate (Aldrich, monomer with Formula (II), 0.0232 mol per 1 mol acrylonitrile), 1.175 mg potassium persulfate (polymerization initiator, from Wako Pure Chemical Industries, Ltd.), 135 mg α-methylstyrene diner (chain-transfer agent, from Wako Pure Chemical Industries, Ltd.), and 450 mL purified water (Wako Pure Chemical Industries, Ltd.) into a 1.0-liter separable flask equipped with a stirrer, thermometer, and reflux condenser. The reaction solution was vigorously stirred for 3 hours at 60° C. and 3 hours at 80° C. After cooling to room temperature, the reaction solution was suction-filtered and the precipitated resin was filtered off. The filtered-off resin was washed in sequence with 300 mL purified water (Wako Pure Chemical Industries, Ltd.) and 300 mL acetone (Wako Pure Chemical Indust...

example 8

[0061] Composite slurries were prepared by mixing amorphous carbon with an average particle size of 20 μm and the binder resin composition-containing varnish prepared in Example 1 (containing 10 mass % binder resin composition) in the range from 99.0 mass %: 10.0 mass % (1.0 mass % as resin fraction) to 95.0 mass %: 50.0 mass % (5.0 mass % as resin fraction) and adding NMP for viscosity adjustment. These were uniformly coated on 10 μm-thick copper foil (current collector), and a sheet-shaped electrode was prepared by then drying for 1 hour in a convection dryer set at 80° C. Seven sheet-shaped electrodes having different resin fractions were prepared in this manner. Each sheet-shaped electrode was pressed with a roll press to prepare an electrode having a composite density of 1.5 g / cm3. The presence / absence of laminate debonding was visually inspected at this point in order to investigate the relationship to the resin fraction (mass %). It is presumed that the absence of laminate de...

example 15

[0064] Lithium manganate with an average particle size of 10 μm, carbon powder with an average particle size of 3 μm, and the binder resin composition-containing varnish obtained in Example 1 (binder resin composition content=10 mass %) were mixed in proportions of 87.0 mass %: 8.7: 43.0 mass % (4.3 mass % as the resin fraction), and a composite slurry was then prepared by the addition of NMP for viscosity adjustment. This slurry was coated and dried onto one side of 20 μm-thick aluminum foil. The composite is coated at the rate of 30 mg / cm2. This was followed by rolling with a roll press to give a composite density of 2.6 g / cm3; cutting into a circle with a diameter of 1.5 cm then gave a sheet-shaped positive electrode. The positive electrode was thereafter obtained by vacuum drying for 16 hours at 120° C. in order to remove residual solvent and adsorbed water in the electrode.

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Abstract

An object of the present invention is to provide a binder resin composition which exhibits excellent adhesion to the negative electrode current collector and an excellent resistance to liquid electrolyte-induced swelling, and which provides an electrode having excellent flexibility and plasticity. Additional objects of the present invention are to provide, through the use of this binder resin composition, an electrode for nonaqueous electrolyte energy devices and a nonaqueous electrolyte energy device, which exhibit a high capacity as well as a smaller capacity fading during charge-discharge cycling. A binder resin composition for a nonaqueous electrolyte energy device electrode comprises a copolymer that contains a repeat unit derived from a nitrile group-containing monomer; a repeat unit derived from a monomer represented by Formula (I)
(wherein R1 is H or CH3; R2 is H or monovalent hydrocarbonyl group; and n is an integer from 1 to 50) and/or a repeat unit derived from a monomer represented by Formula (II)
(wherein R3 is H or CH3 and R4 is hydrogen or C4-100 alkyl); and optionally a repeat unit derived from a carboxyl group-containing monomer.

Description

TECHNICAL FIELD [0001] The present invention relates to a binder resin composition for nonaqueous electrolyte energy device electrodes, to an electrode for nonaqueous electrolyte energy devices, and to nonaqueous electrolyte energy devices. BACKGROUND ART [0002] Lithium ion secondary batteries, which are nonaqueous electrolyte-type energy devices that have high energy densities, are widely used as a power source for portable information terminals such as notebook personal computers, portable phones, and PDAs. [0003] The negative electrode active material used in these lithium ion secondary batteries (referred to hereafter simply as lithium batteries) is a carbon material that has a multilayer structure that has the ability to intercalate the lithium ion between layers (formation of a lithium interlayer compound) and to discharge the lithium ion. A lithium-containing complex metal oxide is primarily used as the positive electrode active material. The electrodes of lithium batteries a...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): H01M4/02C08F20/06C08F20/44H01M4/13H01M10/052H01M10/36
CPCC08F220/18C08F220/24C08F220/28C08F220/44Y02E60/122H01M4/621H01M4/622H01M10/052H01M4/13Y02E60/10C08F220/282C08F220/1812C08L79/00
Inventor SUZUKI, KENJIMASHITA, KIYOTAKAFUKUCHI, IWAONAKAZAWA, SATOSHI
Owner RESONAC CORP
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